I have never used QTP nor Silktest, so I cannot make a comparison.
In my opinion RFT's strong points are (in no particular order):
- Interacts well with the required browsers (IE6, IE8, IE9)
- Object maps with extensive Regular Expression support for handling object recognition and a dynamic find by properties method.
- Java based (I added a lot of external libraries for extending test functionality, interacting with the Operating System and other tools)
- Manual Verification Points (I fetch the base data from a database, xml file, RFT own datasets, etc)
- HTML logs for non-tech people with screenshots, and it's quite structured, I manage all of them with a tool, also good for searching, reporting and so on.
- Scripts can run from command line or managed from other IBM Rational products, like Rational Quality Manager (we have our own tracking software, I wrote some custom tools to handle it)
I found 2 very weak points.
The first is the crappy "Simplified Scripting" that constantly crash/fool up things/delete code without telling you. Disable it.
The second is that sometimes it hangs in some deadlock while reading or writing IE6 memory, but I bet it's more a IE fault ;-)